Pressure control valve

ABSTRACT

A pressure control valve with a valve-closing member which is axially movably guided within a valve housing and which is capable of adjusting a passage between a first pressure agent connection and at least one second pressure agent connection depending on its position being variable in respect of a valve seat, pressure agent transition ducts to be shut off or opened up directly one after the other by the valve-closing member being positioned between the first and the second pressure agent connections for the reduction of the noise of the valve, which said pressure agent transition ducts form a variable cross-sectional area of the valve opening.

TECHNICAL FIELD

The invention relates to pressure control valves, and in particular toelectromagnetic valves for slip-controlled brake units for automotivevehicles.

BACKGROUND OF THE INVENTION

In the German patent application No. 41 03 365.5 a pressure controlvalve being controllable by an electromagnet is described whosetappet-shaped valve-closing member controls the passage between a firstpressure agent connection and a second pressure agent connection in therange of a funnel-shaped valve seat surface depending on the stroke. Forsafeguarding, a pressure-balanced valve actuation and a pressurebalancing duct connect the magnet armature chamber (being shielded) bymeans of a packing seal.

The prior-art valve design generates much noise during the impulse likevalve switching phases. This noise is primarily caused by thevalve-closing member striking against the valve seat and by thenonsteady flow attitude and, thus, the discontinuous flow around thevalve-closing member on account of the binary valve switching positions.

It is, therefore, the object of the invention to improve a pressurecontrol valve of the prior art so that the noise problems are overcomewhile simultaneously guaranteeing reliable operation and a comparativelysimple-design structure.

In accordance with the present invention, the pressure agent transitionducts (to be shut off or to be opened up directly one after the other bythe valve-closing member) are positioned between the first and thesecond pressure agent connections. The pressure agent transition ductshave a cross-sectional area of the valve opening which is variable bysteps.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a cross sectional view of the electromagneticallyactuatable pressure control valve of the present invention with pressureagent transition ducts positioned in the valve seat element; and

FIG. 2 shows an advantageous design version for the positioning ofpressure agent transition ducts within a valve seat.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a valve tappet 11 which in the electromagneticallyde-energized normal position is switched to permanent pressure agentpassage, which is furnished with a valve-closing member 4 and whichcontrols the pressure agent connection between a pressure agent source,for example, coming from a brake pressure master unit, through a firstpressure agent connection 2, and the consumer-side second pressure agentconnection 3 being, for example, connected on the side of the wheelbrake.

A second pressure chamber 12 connecting the first to the second pressureagent connection 2, 3 accommodates a sealing element 14 which seals offthe valve tappet 11 with respect to a first pressure chamber 13. Thesealing element 14 is retained at a front surface of a guide element 16by means of a compression spring 15 which is positioned within thesecond pressure chamber 12. The guide element 16 being retained by meansof caulking between the offset opening within the valve housing 17. Themagnet core 5 preferably has a disc-shaped configuration whose borebeing disposed coaxially is penetrated with play by the valve tappet 11.

In the section of said magnet core 5 facing the guide element 16 thereis a stepped bore for the accommodation of a second spring 15' whichpositions a sealing element 14 on the opposite front surface of theguide element 16, (analogous to the first spring 15). In this way it isguaranteed that notwithstanding a fit dimensioned with a relativelyabundant play between the valve tappet 11 and the bore of the guideelement 16 a sufficient sealing effect between the first pressurechamber and the second pressure chamber comes about.

In this configuration, the first pressure chamber 13 facing the magnetcore 5 extends along the valve tappet 11 into the cavity of the valvedome. A permanent pressure compensation between the consumer-side secondpressure agent connection 3 and the first pressure chamber 13 takesplace through corresponding, transversely extending recesses at thefront surface of the magnet core 5 which contacts the guide element 16and through a ring-shaped recess within the valve housing 17 whichconnects the first pressure chamber 13 to a by-pass duct 18. The sealingelements preferably consist of polytetrafluoroethylene or of acomparable material.

For the autocentration of the valve tappet 11 with respect to the valveseat 8, the sealing elements 14 can move (or slide) in a radialdirection, on the front surface of the guide element 16. This freemobility is fostered, among others, by the directional elasticity freeof transverse force of the compression spring 15. The sealing elements14 are designed such as to be self-sealing under the action of thehydraulic pressure, so that a perfect hydraulic tightness and butminimum frictional forces come about already by comparatively low springforces. Because of the extraordinarily low frictional forces, distinctlyfavorable conditions are present for promoting sliding movement inradial direction. This results in the desired autocentration. Themushroom-shaped valve-closing member 4 is guided within a truncatedcone-shaped valve-supporting element 10. The valve-supporting element10, thus, performs simultaneously the function of a centering device,for which purpose said valve-supporting element 10 is aligned andpreferably retained by caulking in a concentrical position with respectto the valve tappet 11 and to the funnel-shaped valve seat 8 in thevalve housing 17.

The circumferential surface of the valve supporting element 10 ispenetrated by a plurality of pressure agent transition ducts 1, 1'provided with an orifice bore. Ducts 1, 1' are shut one after the otherby the stepped stem of the valve-closing member 4 depending on thestroke. The step-shaped offset of said valve-closing element 4 performsthe function of a restrictor. The original passage being determined bythe opening area of the valve seat will, thus, allow to be controlled incascade, so that a continuous, switchable flow of pressure agent will bebrought about depending on the pressure agent transition ducts 1, 1'being released by the valve tappet 11. In this context, the proportionalcharacteristic of the electromagnet caused by the conical front faces atthe magnet armature and at the magnet core proves particularlyadvantageous. This affords a precise control of the valve tappet strokeand, thus, of the pressure agent passages depending on a variablyadjustable armature current. On one hand, the control quality will beincreased in this way in the sense of a pressure course allowing to beprecisely influenced in the desired manner and, on the other hand, thepressure-balanced design of the valve will contribute to minimizing theactuating forces and, consequently, the armature current. Beyond this, arelatively simple control technique relation results between thearmature current and the area of the passage to be released by steps.

FIG. 2 shows an alternative design version for the positioning and forthe configuration of the pressure agent transition ducts 1, 1'integrated in the valve seat 8. A plurality of pressure agent transitionducts 1, 1' which are disposed one above the other at a defined distanceterminate in the hollow cylinder-shaped section of the valve seat 8. Thepressure agent transition ducts 1, 1' are completely covered by theplunger piston 9 in the illustrated locking position of the plungerpiston 9 being coupled to the valve-closing member 4. The hollowcylinder-shaped section of the valve seat 8 is succeeded by thefunnel-shaped valve seat surface already known from FIG. 1 against whichthe spherical section of the valve-closing member 4 comes to be abutted.The residual components which are required for the actuation of thepressure control valve are identical to the design in FIG. 1, so that arepeated total illustration may be foregone and reference may be made toFIG. 1 in this regard.

The pressure agent transition ducts 1, 1' in FIG. 2 are provided withthe orifices calibrating the flow rate, in analogy with FIG. 1. Theannular groove 19 at the valve seat 8 constitutes a distributing chamberfor the pressure agent which is being conveyed to the first pressureagent transition duct when the conical seat is open. From the annulargroove 19 the pressure agent will then be distributed to the other twopressure agent transition ducts 1, 1' which are furnished with orificesand which end up, through the hollow cylinder-shaped section at thevalve seat 8 being closable by the plunger piston 9, in the pressureagent connection 3 leading to the wheel brake.

According to FIG. 2, the valve-closing member 4 is in theelectromagnetically fully energized closing position, so that allpressure agent transition ducts 1, 1' are closed. In theelectromagnetically de-energized, open normal position of the valve, allpressure agent transition ducts 1, 1' are released by said valve-closingmember, so that an unobstructed connection exists between the first andthe second pressure agent connections 2, 3. As soon as the valve-closingmember 4 initiates a stroke movement the pressure agent transition ducts1, 1' (which end up in the hollow cylinder-shaped section of the valveseat 8) will be shut off one after the other (or sequentially) by thecircumferential surface of the plunger piston acting as a slide valve.As a consequence of the restrictor effect, respectively of the orificeeffect, a gradual, continuous, controlled reduction of the pressureagent flow will take place in the two pressure agent transition ducts 1,1' until finally the pressure agent transition duct connecting theconical sealing seat to the annular groove 19 and being free of anorifice is separated, by the abutment of the spherical section of thevalve-closing member 4 with the valve seat 8, from the second pressureagent connection 3 which is situated above said valve-closing member 4.As already mentioned, assuming a suitable proportional characteristic ofthe electromagnet, the stepwise opening of the pressure agent connectionwill allow the flow of pressure agent to be decisively influenced bycontrolling the armature current. A distinct improvement can be achievedas to the noise behavior which referred to the specific application forslip-controlled brake units in automotive vehicles will lead to adesirable increase of the comfort.

We claim:
 1. A pressure control valve having a valve-closing memberwhich is capable of adjusting a passage between a first pressure agentconnection and at least one second pressure agent connection dependingon its position, comprising:a first pressure chamber and a secondpressure chamber which are isolated from each other by sealing elementsand are arranged directly one after the other between the first and thesecond pressure agent connections, a valve tappet extending through thesealing elements and a guide element, said sealing elements beingarranged sealedly and radially movably on said guide element, the guideelement having a bore for slidably receiving said valve tappet such thatsaid tappet can move axially relative to said guide element, twopressure agent transition ducts provided in one of said first or secondpressure chamber to form a variable cross-sectional area of a valveopening between said first and second pressure agent connections, avalve-supporting element arranged in series relative to a valve seat,said valve-closing member abutting a portion of one of saidvalve-supporting element or said valve seat at one end of an axialtravel of said valve tappet and wherein said transition ducts areprovided in one of said valve-supporting element or said valve seat,arranged in a cascaded axial arrangement such that axial movement ofsaid valve-closing member sequentially opens or closes, depending on thedirection of axial movement, said transition ducts to thereby allowpressure agent to be communicated between the first pressure agentconnection and the second pressure agent connection.
 2. A pressurecontrol valve as claimed in claim 1, wherein said plurality of pressureagent transition ducts are defined through a portion of saidvalve-supporting element.
 3. A pressure control valve as claimed inclaim 1, wherein the pressure control valve is an electromagneticallycontrollable proportional valve including an electromagnetic armaturethat variably adjusts a stroke of the valve-closing member axial travelby a variation of a current within a coil in said electromagneticarmature.
 4. A pressure control valve as claimed in claim 3, whereinsaid proportional valve is hydraulically pressure-balanced, and whereina spring is arranged as a force counteracting the force of saidelectromagnetic armature.
 5. A pressure control valve as claimed inclaim 1, wherein said pressure agent transition ducts are distributedover a plurality of valve stroke sections and are directed toward thevalve-closing member substantially at a right angle to the direction ofsaid axial travel of said valve tappet.
 6. A pressure control valve asclaimed in claim 1, wherein said plurality of pressure agent transitionducts are defined through a portion of said valve seat.
 7. A pressurecontrol valve having a valve-closing member which is capable ofadjusting a passage between a first pressure agent connection and atleast one second pressure agent connection depending on its position,comprising:a first pressure chamber and a second pressure chamber whichare isolated from each other by sealing elements, a valve tappetextending through the sealing elements, said sealing elements beingarranged sealedly and radially movably on a guide element, the guideelement having a bore for slidably receiving the valve tappet, whereinsaid valve-closing member is furnished with a plunger piston having agenerally spherical section that is guided so as to be abuttable againsta valve seat, said generally spherical section of said valve-closingmember having a larger diameter than said plunger piston, and aplurality of pressure transition ducts provided in said valve seat andbeing axially arranged such that axial movement of said plunger pistonrelative to said valve seat sequentially opens or closes said transitionducts, respectively, and wherein said generally spherical section closesoff all of said transition ducts when said spherical section abutsagainst said valve seat.
 8. A pressure control valve as claimed in claim7, wherein said valve seat further comprises a first valve seat surfacewhich is flared funnel-shaped and a cylindrical second slide valvesealing surface which is penetrated by said plurality of pressure agenttransition ducts, which are in sequential axial alignment.
 9. A pressurecontrol valve as claimed in claim 7, wherein the pressure agenttransition ducts are furnished with at least one of an orifice and arestrictor.